title: Classifying idiopathic inflammatory myopathies: comparing the performance of six existing criteria.
abstract: OBJECTIVE
  Various criteria have been proposed to classify the inflammatory myositides (IIMs) polymyositis (PM) and dermatomyositis (DM). However, none have received universal acceptance. Our aim was to assess the performance of the main criteria used to classify IIM. Specialist consultant diagnosis was considered the gold standard.
  
  
  METHODS
  Patients attending King's College Hospital (KCH) or Reggio Emilia Hospital (REH) since 1990 with a diagnosis of IIM or non-inflammatory myopathy were identified, and their records and laboratory investigations retrospectively reviewed. Where the complete data required for the classification criteria or a final physician diagnosis was unavailable, patients were excluded. 52 patients with a specialist diagnosis of PM, DM, inclusion body myositis (IBM) or non-inflammatory myopathy were included. Agreement between specialist consultant diagnosis and classification criteria was measured using Cohen's kappa (κ) statistics. Sensitivity and specificity were also calculated.
  
  
  RESULTS
  The Dalakas (2003) criteria demonstrated substantial agreement with specialist diagnosis: κ=0.69, sensitivity 77%, specificity 99%. The European Neuromuscular Centre criteria (ENMC) demonstrated fair agreement: κ=0.49, sensitivity 71%, specificity 82%. Other criteria performed less well. In particular, the Bohan and Peter criteria demonstrated a specificity of only 29%.
  
  
  CONCLUSIONS
  The criteria of Dalakas (2003) agreed best with specialist consultant diagnosis. The criteria of Bohan and Peter demonstrated very poor specificity. Prospective studies are required to develop improved classification criteria.
authors.affiliation: Department of Rheumatology, King's College Hospital NHS Foundation Trust, London SE5 9RS, UK. helenlinklater@doctors.org.uk.
authors.forename: Helen
authors.initials: H
authors.lastname: Linklater
authors.forename: Nicolò
authors.initials: N
authors.lastname: Pipitone
authors.forename: Michael R
authors.initials: MR
authors.lastname: Rose
authors.forename: Fiona
authors.initials: F
authors.lastname: Norwood
authors.forename: Richard
authors.initials: R
authors.lastname: Campbell
authors.forename: Carlo
authors.initials: C
authors.lastname: Salvarani
authors.forename: D L
authors.initials: DL
authors.lastname: Scott
authors.forename: Patrick
authors.initials: P
authors.lastname: Gordon
mesh_terms: D015415:Biomarkers / Q000097:blood; D001706:Biopsy; D003882:Dermatomyositis / Q000097:blood / Q000145:classification / Q000175:diagnosis*; D004576:Electromyography; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D007558:Italy; D008131:London; D008297:Male; D008875:Middle Aged; D010808:Physical Examination; D017285:Polymyositis / Q000097:blood / Q000145:classification / Q000175:diagnosis*; D011237:Predictive Value of Tests; D012017:Referral and Consultation; D012189:Retrospective Studies; D012720:Severity of Illness Index
chemical_list: D015415:Biomarkers